Interpretive Summary: Ultra low volume (ULV) sprays are most commonly used to control insects, such as mosquitoes, that can adversely affect public health. Effective application of ULV sprays is highly dependent on properly assessing the spray generated by a sprayer. Because there are several types of samplers to assess sprays, comparative assessment of sprayers is needed for the same application and environmental conditions. Replicated field studies were conducted with five different samplers simultaneously placed downwind of an ULV sprayer to measure the concentration of the spray cloud up to 90 m from the sprayer. Based on the results of this experiment, use of the horizontal and rotating cotton ribbons are recommended for measuring deposition during evaluation of ULV space sprays. These measurements should help to calculate more accurately the amount of spray required to effectively control disease carrying insects with ULV sprays.

Technical Abstract:
A field study was conducted to investigate the suitability of sampling devices for quantification of spray deposition from ULV space sprays. Five different samplers were included in an experiment conducted in an open grassy field. Samplers included horizontally stretched stationary cotton ribbon at two heights above ground, rotating ribbons, rotating glass slides, and filter paper for ground deposition. Rotating slides were also used for droplet size measurements. One of each sampler type was placed at 7 downwind locations: 1, 7, 15, 25, 40, 65, and 90 m from the spray line. Applications of water and mineral oil mixed with suitable fluorescent dyes as tracers were made with a truck mounted ULV sprayer at dusk and dawn. Results suggest that horizontal and rotating cotton ribbons can be used for quantification of ULV space sprays, while filter paper can be used for estimation of ground deposition. Droplets on rotating slides were detected only for the oil based sprays. Stationary ribbons are useful if quantification of spray flux at various heights is desired; otherwise, the rotating ribbon is a better choice. The logistics of any experiment will affect the choice of a sampler type.